Metal accumulation in eggs of the red-eared slider ( Trachemys scripta elegans) in the Lower Illinois River

Abstract

The Illinois River is a highly utilized navigable waterway in the US Midwest, and has historically been contaminated with metal toxicants from various industrial and municipal pollution sources. Little information on metal contamination is available in the Lower Illinois River, and in particular, in the habitat of the red-eared slider ( Trachemys scripta elegans) at the southern end of the river near Grafton, IL. This study was conducted to determine current levels of metal contamination in water, sediment, soil, and plants in the habitat, as well as to reveal temporal and spatial variations of metal accumulation in eggs of the red-eared slider. Aluminum, Cd, Cr, Cu, Mn, Ni, Pb, V, Sn, and Zn were analyzed by inductively-coupled plasma spectroscopy. High concentrations of metals were observed in lake sediment, compared with the concentrations in water, soil, and plant tissues. Sediment Ni concentrations (mg kg −1) varied from 66 to 95 and Sn from 1100 to 1600. Five detectable metals in egg content were Zn (24.2 ± 13), Al (2.2 ± 1.2), Sn (1.8 ± 1.1), Mn (1.1 ± 0.6), and Cu (0.9 ± 0.5); nine detectable metals in egg shell were Zn (6.8 ± 3.9), Sn (3.7 ± 3.1), Cu (1.9 ± 1.3), Cr (1.6 ± 1.5), V (1.6 ± 1.4), Pb (1.3 ± 0.7), Ni (1.3 ± 0.9), Mn (1.0 ± 0.8), and Cd (0.16 ± 0.11). Zinc accumulation in egg content was significantly correlated with Zn in egg shell ( r = 0.445, P < 0.002, n = 42). While significant spatial variation was observed in egg shell, metal accumulation in eggs (content and shell) collected from the same ground of turtles consecutively for 4 years did not show a significant temporal change.